The most puncture-resistant tubular I can think of is a Vittoria Rally. I would never mount one on a race wheel, though.....way too slow. You'd be negating a good chunk of the aero benefits you'd otherwise be getting from having an aero wheel. I just take the chance of getting a flat. It won't happen often, and a lot of times you can get a flat no matter how "puncture-resistant" your tire is (I've sliced up several Armadillos).

That said, the Vittoria Triathlon has pretty much no protection at all, so I don't use it. I run Vittoria Corsa Evo KS's on both my sets of aero wheels. The guy I shared my homestay with at Memphis in May this year hates them, though. They do leak faster than other tires (I never thought of it being a problem since I just inflate them on race morning). He uses Continental Sprinters instead. I've run those, too.....also very good tires. I'm not a fan of Tufos (and I know a lot of people that feel the same). They just don't ride as nicely as other tires. They're rough, and I've heard that they have a pretty high rolling resistance. I'd go with Vittoria Corsa Evos (not the tri ones...the KS model has the lowest rolling resistance after those) or some Conti Sprinters, Conti Competitions, etc. (not the Conti Podiums....they're a lot like the Vittoria Triathlons).

The CX's are very similar to the KS. The CX's have a slightly higher rolling resistance, but are usable in the rain (KS's kind of aren't). That should be pretty self explanatory after looking at each tire's tread pattern, though. Good luck.

I have Tufo Giro Twix that I use for road racing and training and have never had a problem. They're super smooth, and awesome in wet. Have about 1k miles on my current set glued to Bonti Race X Lites and have only needed to re-inflate once in 2 months. They seem to be pretty good when it comes to punctures too. I've hit just about everything in Chicago and still rolling perfectly.
I have tufo elites on my TT wheels, partially because they're blue to match my frame, but mostly because they're absurdly light and fast. Better than the vittorias I've ridden.
You may also want to check into the Conti GP 4000's. I had a set of 3000 clinchers on an old road bike that rolled beautifully, and I can only imagine the feel of riding them in tubular form. Never punctured with the 3000's.

second the conti comps. so far so good for me-- great tires!

Actually, I've been seeing stuff lately that says narrower tires DON'T necessarily have a lower rolling resistance. Obviously a 22mm tire is going to be faster than a 35mm tire, but the 22mm tire might also be faster than the 19 as well. I'm not sure about the physics on this one, but I've heard it more than one place (sorry, no link). Super-thin tires are more of a track-racing thing (just like running your tires at 160+ psi.....there's a sweet spot for road riding at about 130 psi depending on your weight.....just like a sweet spot in tire size at about 21-22mm to optimize rolling resistance).

Generally, a thinner tire will be more prone to pinch flats, but because you're running tubulars, this really isn't a concern.

Most aero wheels are designed to have the best drag numbers with the thinnest tire. I know that Zipps are actually optimized for a 21mm tire. I don't know what kind of wheels you have. If you have Zipps, I'd say 100% use the 22mm.

The 22s will be more supple. This could help dampen road vibration and help save your legs, especially if the road is rough.

I'd bet that if you were able to run both back-to-back, you'd say the 19s were faster--partly due to the fact that you'd have to run them at a higher pressure (which doesn't make them faster....just makes the ride rougher and creates the feeling of being faster). However, I'd bet that the lower rolling resistance and comfort of the 22s would outweigh an aero loss compared to the 19s (assuming you're not running Zipps). I'd go with 22s either way.